you cant only migrating them and catching them in pal park ruby sapphire emerald and maby more
Yes First, you need to have a Regirock/Registeel/Regice in your party.
Regice, Regirock, and Registeel are unobtainable through normal gameplay in Pokemon X or Y. The only way to get them (without cheating) is to receive them in a trade with another player or transfer them through PokeBank/PokeTransporter from an old game. As of September 19th, 2014, there have been no events announced where you can get Regice, Regirock, or Registeel.
Here are all the legendaries you can get without cheats: Groudon, Kyogre, Regice, Regirock, Registeel, Rayquaza, Latios/Latias.
Latios, groudon, Rayquaza, Regice, regirock, registeel, they are the legendaries you catch int he game without cheating or trading
you cant. regice regirock and registeel are all part of the hoen pokedex
yes
Yes, you can trade for it or you can mirage it into the Pal Park from the GBA Pokemon games.
get regice regirock and registeel and go to snowpoint temple
Kyogre and regirock-regice-registeel
Sorry but you have to catch Regice, Registeel and Regirock in order to catch Regigigas.
you can't in diamond without migration, however you can get them in platinum by trading the event lvl 100 regigigas form diamond or pearl to platinum, then they will appear in certain rooms that were once empty. Regice: in mt. coronet on the way to snowpoint city Registeel: at the final room on iron island before you go outside Regirock: unknown. sorry is that for platimun or diamod??
You cannot get Regirock in Diamond without migrating one from Ruby, Sapphire or Emerald.